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virtio-input: fix eventq batching

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virtio_input_send buffers input events until it sees a SYNC. Then it
either sends or drops the entire batch, depending on whether eventq
has enough space available. The case to avoid here is partial sends
where only part of the batch would get to the guest.

Using virtqueue_get_avail_bytes to check the state of eventq was not
correct. The queue may have a smaller number of larger buffers
available so bytes may be enough but the batch would still not be
possible to send, leading to the "Huh?  No vq elem available" error.

Instead of checking available bytes, this patch optimistically pops
buffers from the queue and puts them back in case it runs out of
space and the batch needs to be dropped.

Signed-off-by: Ladi Prosek <lprosek@redhat.com>
Message-id: 1490365490-4854-3-git-send-email-lprosek@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Ladi Prosek 2017-03-24 15:24:50 +01:00 committed by Gerd Hoffmann
parent 0f5a15e40a
commit 57094547df
2 changed files with 19 additions and 17 deletions
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25
hw/input/virtio-input.c
View File

@ -22,7 +22,6 @@
void virtio_input_send(VirtIOInput *vinput, virtio_input_event *event)
{
VirtQueueElement *elem;
unsigned have, need;
int i, len;
if (!vinput->active) {
@ -33,9 +32,9 @@ void virtio_input_send(VirtIOInput *vinput, virtio_input_event *event)
if (vinput->qindex == vinput->qsize) {
vinput->qsize++;
vinput->queue = g_realloc(vinput->queue, vinput->qsize *
sizeof(virtio_input_event));
sizeof(vinput->queue[0]));
}
vinput->queue[vinput->qindex++] = *event;
vinput->queue[vinput->qindex++].event = *event;
/* ... until we see a report sync ... */
if (event->type != cpu_to_le16(EV_SYN) ||
@ -44,24 +43,24 @@ void virtio_input_send(VirtIOInput *vinput, virtio_input_event *event)
}
/* ... then check available space ... */
need = sizeof(virtio_input_event) * vinput->qindex;
virtqueue_get_avail_bytes(vinput->evt, &have, NULL, need, 0);
if (have < need) {
for (i = 0; i < vinput->qindex; i++) {
elem = virtqueue_pop(vinput->evt, sizeof(VirtQueueElement));
if (!elem) {
while (--i >= 0) {
virtqueue_unpop(vinput->evt, vinput->queue[i].elem, 0);
}
vinput->qindex = 0;
trace_virtio_input_queue_full();
return;
}
vinput->queue[i].elem = elem;
}
/* ... and finally pass them to the guest */
for (i = 0; i < vinput->qindex; i++) {
elem = virtqueue_pop(vinput->evt, sizeof(VirtQueueElement));
if (!elem) {
/* should not happen, we've checked for space beforehand */
fprintf(stderr, "%s: Huh? No vq elem available ...\n", __func__);
return;
}
elem = vinput->queue[i].elem;
len = iov_from_buf(elem->in_sg, elem->in_num,
0, vinput->queue+i, sizeof(virtio_input_event));
0, &vinput->queue[i].event, sizeof(virtio_input_event));
virtqueue_push(vinput->evt, elem, len);
g_free(elem);
}

5
include/hw/virtio/virtio-input.h
View File

@ -62,7 +62,10 @@ struct VirtIOInput {
VirtQueue *evt, *sts;
char *serial;
virtio_input_event *queue;
struct {
virtio_input_event event;
VirtQueueElement *elem;
} *queue;
uint32_t qindex, qsize;
bool active;